In a mail handling system, as, for example, in the United States Postal Service, the majority of mail traffic consists of ordinary business-size envelopes and large (bulk mail) parcels. They are handled by automatic machinery which accepts mail pieces falling within a specific range of sizes and shapes. There is a residue, however, that cannot be handled by existing machinery. This residue comprises a few percent of the immense mail volume and its handling is, therefore, a significant problem costing hundreds of millions of dollars each year.
One category of this residual mail is known as "irregular pieces and parcels" which includes small boxes, film mailers, rolled newspapers, tubes, hotel keys, small bags, etc. Another group, referred to as "flats", consists of generally flat mail pieces such as tabloid weekly newspapers, magazines, oversized envelopes, packs of inquiry cards, and stuffed envelopes containing, for example, bank statements with return checks. Open magazines, without sleeves, are especially difficult to handle by machine. This type of mail includes much of the periodical and advertising mail, which accounts for little revenue but which requires a large labor force for processing.
In the handling of these irregular mailpieces, there is quite obviously a need for automation in order to provide speedy, accurate and cost-effective processing. In particular, when an agglomeration of these mailpieces is presented for destination coding by an operator, it would be advantageous to separate the individual items from the heap, locate the zip code, present the stamp face up for cancellation, present the zip code to an operator who keys it into the system, and dispatch it into an appropriate hamper with items having a similar destination.
The process of separating one mailpiece from a pile is referred to as singulation. There have been attempts to singulate irregular mailpieces by variations of conventional material handling techniques, e.g., differential motion or spreading. These techniques work well when the machines are designed for a uniform stream of a known article. However, they became less than efficient for uncontrolled mixes of unpredictable articles. One mail singulation system for automatically singulating irregular mail is disclosed in U.S. Pat. No. 4,634,28, issued Jan. 6, 1987, to R. M. Carrell. In this system a robotic arm operated in conjunction with a machine vision apparatus, pushes individual articles from heap onto a take away conveyor.